V. de Zea Bermudez

Full‐Color Phosphors from Amine‐Functionalized Crosslinked Hybrids Lacking Metal Activator Ions

Sol–gel derived hybrids that contain OCH2CH2 (polyethylene glycol, PEG) repeat units grafted onto a siliceous backbone by urea, –NHC(=O)NH–, or urethane, –NHC(=O)O–, bridges have been prepared. It is demonstrated that the white light PL of these materials results from an unusual convolution of a longer lived emission that originates in the NH groups of the urea/urethane bridges with shorter lived electron–hole recombinations occurring in the nanometer-sized siliceous domains. The PL efficiencies reported here (maximum quantum yields at room temperature of ≈ 0.20 ± 0.02 at a 400 nm excitation wavelength) are in the same range as those for tetramethoxysilane–formic acid, and APTES–acetic acid, sol–gel derived phosphors. The high quantum yields combined with the possibility of tuning the emission to colors across the chromaticity diagram present a wide range of potential applications for these hybrid materials.

A novel class of luminescent polymers obtained by the sol–gel approach

A series of amorphous Eu3+-doped hybrid organic/inorganic materials prepared by the sol–gel process is presented. The host matrix of the so-called ureasils is a silica network to which oligopolyoxyethylene chains are grafted by means of urea bonds. Trivalent europium is present as a triflate salt, Eu(CF3SO3)3. Four different compositions of salt have been considered: n=184, 92, 55 and 37, where n represents the number of (OCH2CH2) polymer repeat units per ion group of Eu(CF3SO3)3. Infrared spectroscopic studies suggest that the doped ureasils contain both free and coordinated triflate ions. The lowest decomposition temperature (about 250°C) occurs with composition n=92. This composition also exhibits the highest conductivity at room temperature (approximately 10−5 Ω−1 cm−1). The photoluminescence spectra of these materials present a series of narrow lines assigned to 5D0→7F0,1,2,3,4 transitions. The high emission intensity observed is a promising property for application of the ureasils in technological luminescent devices.

Synthesis and characterization of novel urethane cross-linked ormolytes for solid-state lithium batteries

Abstract A novel family of Li + -based organic/inorganic materials obtained by the sol–gel process is proposed. The compounds, named urethanesils , are obtained as thin, transparent, elastomeric and amorphous monolithic films. They incorporate solvating pendant methyl end-capped short poly(oxyethylene) chains which are covalently bonded to the silica backbone by means of urethane cross-links. The urethane linkages are formed by reacting 3-isocyanatepropyltriethoxysilane with hepta(ethylene glycol) methyl ether (HEGME). Li + has been introduced in the urethanesils as lithium triflate (LiCF 3 SO 3 ). Two compositions of salt have been considered: n =100 and 8, where n represents the molar ratio of (OCH 2 CH 2 ) units per lithium ion. Infrared spectroscopy provides conclusive evidence that, although the oligopolyether chains of HEGME become less disordered upon formation of the inorganic network, the addition of salt induces disorder. The FTIR spectrum of the most concentrated urethanesil strongly suggests that the triflate ions are essentially coordinated in the material. The thermal and mechanical properties of the undoped and doped urethanesils have been investigated by DSC and DMTA. At 90°C, the highest ionic conductivity (approximately 10 −6 Ω −1 cm −1 ) is observed for composition n =8. The electrochemical stability domain of the least concentrated urethanesil spans 5 V.

Enhanced emission from Eu(III) β-diketone complex combined with ether-type oxygen atoms of di-ureasil organic-inorganic hybrids

Abstract Organic–inorganic hybrids, named di-ureasils and described by polyether-based chains grafted to both ends to a siliceous backbone through urea cross linkages, were used as hosts for incorporation of the well-known coordination complex of trivalent europium (Eu 3+ ) ions described by the formula [Eu(TTA) 3 (H 2 O) 2 ] (where TTA stands for thenoyltrifluoroacetone). By comparing with Eu 3+ -doped di-ureasil without complex form the new materials prepared here enhanced the quantum efficiency for photoemission of Eu 3+ ions. The enhancement can be explained by the coordination ability of the organic counterpart of the host structure which is strong enough to displace water molecules in [Eu(TTA) 3 (H 2 O) 2 ] from the rare earth neighbourhood after the incorporation process. High intensity of Eu 3+ emission was observed with a low non-radiative decay rate under ultraviolet excitation. The quantum efficiency calculated from the decay of 5 D 0 emission was 74%, which in the same range of values previously obtained for the most efficient Eu 3+ coordination compounds reported in literature. Luminescence, X-ray absorption and infrared absorption results considered together leads to a picture where the first coordination shell of Eu 3+ is composed of the 6 oxygen atoms of the 3 β-diketonate ligands and 2 ether-like oxygen atoms of the host.

An interesting ligand for the preparation of luminescent plastics: The picrate ion

Electrolytes formed with poly(oxyethylene), POE, and europium picrate, [Eu(pic)2(OH2)6]pic.6H2O (where pic denotes the picrate anion) or simply Eu(pic)3xH2O, have been investigated by infrared and photoluminescence spectroscopies. The complexes have been represented by POEnEu(pic)3xH2O (where n represents the molar ratio of (OCH2CH2) units per Eu3+ ion). Materials with n ranging from 133 to 11 have been examined. A tentative attribution for the absorption bands of the mid-infrared spectra is presented. The spectral changes detected in the mid-infrared region and the modifications observed in the XRD patterns at increasing salt content show that Eu(pic)3xH2O exerts an effective plasticizing role which leads to the complete supression of crystallinity at n=11. The emission spectra of the complexes and their signature in the νC–O spectral region provide conclusive evidence that the Eu3+ ions are coordinated to the oxygens atoms of the polyether chains over the whole range of compositions studied. The photolu...

Thermal properties and ionic conductivities of lanthanide-based ormolytes

Abstract Hybrid organic/inorganic networks doped with europium triflate, Eu(CF 3 SO 3 ) 3 , have been prepared by the sol-gel method and characterized by conductivity and thermal analysis techniques. The electrolyte films produced were obtained as transparent, amorphous monoliths with encouraging optical characteristics and moderate bulk conductivities.

Morphological and conductivity studies of di-ureasil xerogels containing lithium triflate

AbstractSol / gel derived poly(oxyethylene)/siloxane hybrids doped with lithium triflate, LiCF 3 SO ,have been investigated. The hosthybrid matrix of these materials, named di-ureasil and represented by U(600), is composed by a siliceous framework to whichpolyether chains containing 8.5 oxyethylene repeat units are covalently bonded through urea linkages. Xerogel samplesU(600) n LiCF 3 SO 3 with n (where n is the molar ratio of oxyethylene moieties per Li ion) between and 0.1 have beenexamined. X-ray diffraction and differential scanning calorimetry have provided conclusiveevidence that the xerogels analyzed areentirely amorphous. The salt-rich material with n / 1 exhibits the highest conductivity over the whole range of temperature analyzed(e.g. 4.3 6 / 10 and 2.0 / 10 4 V 1 cm , respectively, at 25 and 94 8C). # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Di-ureasils; Li ; X-ray diffraction; Differential scanning calorimetry; Ionic conductivity 1. IntroductionHighly conducting, thin, solvent-free electrolyte filmsmay be produced by dissolving salts in high molecularweight polymers carrying adequate coordinating species,such as ether oxygen atoms or amine nitrogen atoms [1

Water-mediated structural tunability of an alkyl/siloxane hybrid: from amorphous material to lamellar structure or bilamellar superstructure

Mono-amide cross-linked alkyl/siloxane hybrids (classed as mono-amidosils and represented by the notation m-A(x), where m and A stand for mono and amide, respectively, and x is the number of methylene repeat units) with water-mediated tunable structures have been prepared by means of sol–gel chemistry and self-direct assembly routes from the organosilanes CH3(CH2)x–C(O)NH–(CH2)3–Si–(OCH2CH3)3. The amorphous sample m-A(8) has been produced under the stoichiometric conditions (molar ratio Si : ethanol : water = 1 : 4 : 2) used previously to obtain the lamellar bilayer highly organized m-A(14) hybrid material, showing that the length of the pendant alkyl chains affects the degree of order of the materials. Three structurally ordered samples identified as AC-m-A(8) (1 : y) (where AC represents acid catalysis and y is the number of moles of water per mole of Si) have been obtained using the acid catalyzed hydrolytic route and different water contents (y = 600, 300 and 100). Water plays a unique role in the organized mono-amidosils: it not only reverses the natural tendency of the precursor molecule with x = 8 to yield a disordered material, but it also allows the induction of order, leading to the formation of a lamellar structure exclusively in AC-m-A(8) (1 : 100). The presence of a higher water content promotes extra ordering in AC-m-A(8) (1 : 300) and AC-m-A(8) (1 : 600), where the lamellar structure coexists with a bilamellar superstructure. Upon heating the AC-m-A(8) (1 : 600) sample to 120 °C and then cooling it to room temperature, the lamellar structure remained unaffected, while the superstructure was destroyed. The occurrence of the superstructure, although basically associated with the preferential entrapment of water molecules every two lamellae at the siliceous nanodomains, is also correlated with the amide–amide hydrogen bonded array. The m-A(8) and AC-m-A(8) (1 : 600) hybrids are multi-wavelength emitters under UV/VIS excitation. The emission spectra exhibit a broad band (300–650 nm) resulting from two contributions: a “blue” band, due to electron–hole recombinations in the NH/CO groups of the amide cross-links, and a “purplish-blue” band, due to oxygen-related defects •O–O–Si≡(CO2) in the siliceous nanoclusters. The absolute emission quantum yields determined for m-A(8) and AC-m-A(8) (1 : 600) in the 360–380 nm excitation wavelength range were 0.10 ± 0.01 and 0.15 ± 0.01, respectively. While the lifetime values of the high and low wavelength components of the siliceous-related emission are practically the same for both samples (∼3.5 ms), the lifetime value of the NH/CO component for m-A(8) is higher than that of AC-m-A(8) (1 : 600) (∼292 and ∼156 ms, respectively), suggesting a lower non-radiative transition probability for the former hybrid.

K+-doped poly(ε-caprolactone)/siloxane biohybrid electrolytes for electrochromic devices

Sol-gel derived KCF3SO3-doped di-urethane cross-linked poly(-caprolactone) (PCL(530))/siloxane ormolytes with  > n  0.5 (n indicates the number of (C(=O)(CH2)5O) repeat units per K + ion) have been studied. Xerogel samples with n ≥ 1 are thermally stable up to 235 oC. A minor proportion of PCL crystallites occur in some dilute-to-concentrated samples. At n ≤ 4 a crystalline PCL(530)/siloxaneKCF3SO3 complex with unknown stoichiometry emerges. At n ≤ 2 this complex coexists with pure salt. At temperatures higher than 40 oC the composition which exhibits the highest ionic conductivity is n = 21. “Free” anions, weakly coordinated CF3SO3 ions, contact ion pairs and several higher ionic aggregates emerge in all the * Phone: 00-351-259-350253; Fax: 00-351-259-350480; E-mail: vbermude@utad..pt

Sol–gel-derived POE/siliceous hybrids doped with Na+ ions: morphology and ionic conductivity

Abstract Hybrid materials produced by the versatile sol–gel process with a wide sodium triflate, NaCF 3 SO 3 , concentration range have been studied. The host matrix of these xerogels, designated as di-ureasil and represented by U(600), is composed by a siliceous network bonded through covalent bonds to short polyether chains by means of bridging urea groups. The results obtained reveal that at high salt concentration, this system forms crystalline phases. The most conducting ormolyte exhibits a conductivity of 3.6×10 −7 Ω −1 cm −1 at room temperature.